Photographic products and processes

ABSTRACT

THE PRESENT INVENTION RELATES TO PHOTOGRAPHY AND, MORE PARTICULARLY, TO REFLECTION TYPE DIFFUSION TRANSFER PROCESS PHOTOGRAPHIC FILM UNITS WHICH COMPRISE A COMPOSITE PHOTOSENSITIVE ELEMENT ADAPTED TO PROVIDE, BY DIFFUSION TRANSFER PHOTOGRAPHIC PROCESSING, SELECTIVE INTEGRAL NEGATIVE AND POSITIVE IMAGE RECORDATION OF INCIDENT ANTINIC RADIATION AS A FUNCTION OF THE POINT-TO-POINT DEGREE OF PHOTOSENSIVE ELEMENT EXPOSURE, WHICH INCLUDES A PLURALITY OF SEQUENTIAL LAYERS INCLUDING A PHOTOSENSIVE SILVER HALIDE LAYER HAVING ASSOCIATED THEREWITH IMAGE-FORMING MATERIAL WHICH IS PROCESSING COMPOSITION DIFFUSIBLE AT A FIRST PH AS A FUNCTION OF THE POINT-TO-POINT DEGREE OF SILVER HALIDE LAYER EXPOSURE TO INCIDENT ACTINIC RADIATION, A LAYER ADAPTED TO RECIEVE IMAGE-FORMING MATERIAL DIFFUSING THERETO, AND WHICH ADDITIONALLY INCLUDES MEANS FOR PROVIDING AT LEAST ONE OPTICAL FILTER AGENT AT A PH ABOVE THE PKA OF THE OPTICAL FILTER AGENT WHOSE PKA IS BELOW SAID FIRST PH IN A CONCENTRATION EFFECTIVE TO PROVIDE, IN SITU, A LAYER EXHIBITING OPTICAL TRANSMISSION DENSITY SUFFICIENT TO PROVIDE A BARRIER WITH RESPECT TO INCIDENT VISIBLE RADIATION SUBSEQUENT TO PHOTOEXPOSURE OF THE SILVER HALIDE LAYER AND MEANS FOR REDUCING THE INITIAL PH OF THE LAYER TO A SECOND PH BELOW THE PKA OF THE OPTICAL FILTER AGENT, WHICH PH IS ABOVE THE PH NECESSARY FOR DIFFUSION OF SAID IMAGEFORMING MATERIAL AND, SUBSEQUENT TO SUBSTANTIAL TRANSFER IMAGE FORMATION IN THE RECEPTION LAYER, REDUCING THE PH TO A THIRD PH WHEREIN THE IMAGE-FORMING MATERIAL IS NONDIFFUSIBLE.   D R A W I N G

2, 1973 T. w. MILLIGAN 3,734,727

PHOTOGRAPHIC PRODUCTS AND PROCESSES Filed Oct. 28, 1971 4 Sheets-Sheet 1INVENTOR.

TERRY W. MILLIGAN BY filwumamdm and May 22, 1973 w MILLIGAN 3,734,727

PHOTOGRAPHIC PRODUCTS AND PROCESSES Filed Oct. 28, 1971 4 Sheets-Sheet zTERRY W. MILLIGAN 'Mu/ n m p o o 5.

A? TORNEY May 22, 1973 T. w MILLIGAN 3,734,727

PHOTOGRAPHIC PRODUCTS AND PROCESSES Filed Oct. 28, 1971 4 Sheets-Sheet 3INVENTOR. TERRY W. MlLLlGAN BY 0W mm and 1 8.

T TORNE Y y 1973 T. w MILLIGAN 3,73

PHOTOGRAPHIC PRODUCTS AND PROCESSES Filed Oct. 28, 1971 4 Sheets-Sheet 452 .EumEwEE 55 muoiw/ 523 29325 3.3: 536 w Ewzww zuum@ 52 29335 83$. 535uztmzwm Sex F United States Patent Office US. Cl. 96-29 D "41 ClaimsABSTRACT OF THE DISCLOSURE The present invention relates to photographyand, more particularly, to reflection type diffusion transfer processphotographic film units which comprise a composite photosensitiveelement adapted to provide, by diffusion transfer photographicprocessing, selective integral negative and positive image recordationof incident actinic radiation as a function of the point-to-point degreeof photosensitive element exposure, which includes a plurality ofsequiential layers including a photosensitive silver halide layer havingassociated therewith image-forming material which is processingcomposition diifusible at a first pH as a function of the point-to-pointdegree of silver halide layer exposure to incident actinic radiation; alayer adapted to receive image-forming material diffusing thereto; andwhich additionally includes means for providing at least one opticalfilter agent at a pH above the pK, of the optical filter agent whose pKis below said first pH in a concentration effective to provide, in situ,a layer exhibiting optical transmission density sufficient to provide abarrier with respect to incident visible radiation subsequent tophotoexposure of the silver halide layer and means for reducing theinitial pH of the layer to a second pH below the pK,, of the opticalfilter agent, which pH is above the pH necessary for diffusion of saidimageforming material and, subsequent to substantial transfer imageformation in the reception layer, reducing the pH to a third pH whereinthe image-forming material is nondiffusible.

CROSS REFERENCE TO OTHER APPLICATIONS This application is acontinuation-in-part of application Ser. Nos. 83,479 and 83,480, bothfiled Oct. 23, 1970 and both now abandoned.

BACKGROUND OF THE INVENTION (1) Field of the invention The presentinvention is directed to providing new and improved reflection typediffusion transfer process photographic film units which comprise acomposite photosensitive element adapted to provide, as a function ofthe point-to-point degree of photoexposure, integral negative andpositive images which include a negative image in a superposedrelationship with and optically masked from a positive image adapted tobe viewed by reflected light.

(2) Description of the prior art Various film units for forming a colortransfer image viewable, without separation from the remainder of thefilm unit, as a color reflection print, have heretofore been disclosedin the art. Such film units generally comprise a plurality of essentiallayers including at least one lightsensitive silver halide layer andassociated dye imageproviding material and a dyeable stratum. These filmunits also contain means for providing a reflecting layer between thedyeable stratum and the next adjacent silver halide layer and associateddye image-providing material to effectively mask the negative imageformed upon development of the film unit and any remaining dyeimageproviding material and to provide a background for view- 3,734,727Patented May 22, 1973 ing a color transfer image formed in the dyeablestratum, whereby the resulting composite print including the colortransfer image may be viewed, by reflected light, without separation, asa reflection print. These essential layers preferably also include aneutralizing layer to reduce the pH following substantial dye transferto a pH wherein the image-providing material is nondiffusible. Theessential layers may be, and preferably are contained between a pair ofdimensionally stable layers, at least the one closest to the dyeablestratum being substantially transparent to permit viewing therethroughof the resulting transfer image.

As disclosed in US. Pat. No. 3,415,644, a composite photosensitivestructure, particularly adapted for reflection type photographicdiffusion transfer color process employment, which comprises a pluralityof essential layers including, in sequence, a dimensionally stableopaque layer; one or more silver halide emulsion layers havingassociated therewith dye image-providing material for providing animagewise distribution of a dye which is soluble and diffusible, inalkali, at a first pH, as a function of the point-to-point degree of itsassociated silver halide emulsions exposure to incident actinicradiation; a polymeric layer adapted to receive solubilized dyeimage-providing material diffusing thereto; a polymeric layer containingsuflicient acidifying capacity to effect reduction of a processingcomposition from the first pH to a second pH at which the dyeimage-providing material is substantially nondiffusible; and adimensionally stable transparent layer, may be exposed to incidentactinic radiation and processed by interposing, intermediate the silverhalide emulsion layer and the reception layer, an alkaline processingcomposition possessing the first pH and containing opacifying agent,which may reflect incident radiation, in a quantity suflicient to maskdye image-providing material associated with the silver halide emulsion.

In a preferred embodiment, the composite photosensitive structureincludes a rupturable container, retaining the alkaline processingcomposition having the first pH and opacifying agent, fixedly positionedextending transverse a leading edge of the composite structure in orderto effect, upon application of compressive pressure to the container,discharge of the processing composition intermediate the opposedsurfaces of the reception layer and the next adjacent sliver halideemulsion.

The liquid processing composition distributed intermediate the receptionlayer and the silver halide emulsion, permeates the silver halideemulsion layers of the composite photosensitive structure to initiatedevelopment of the latent images contained therein resultant fromphotoexposure. As a consequence of the development of the latent images,dye image-providing material associated with each of the respectivesilver halide emulsion layers is individually immobilized as a functionof the point-to point degree of the respective silver halide emulsionlayer photoexposure, resulting in imagewise distribution of mobile dyeimage-providing materials adapted to transfer, by diffusion, to thereception layer to provide the desired transfer dye image. Subsequent tosubstantial dye image formation in the reception layer, a sufficientportion of the ions of the alkaline processing composition transfers, bydiffusion, to the polymeric neutralizing layer to effect reduction inthe alkalinity of the composite film unit to the second pH at which dyeimage-providing material is substantially nondiifusible, and further dyeimage-providing material transfer is thereby substantially obviated.

The transfer dye image is viewed, as a reflection image, through thedimensionally stable transparent layer against the background providedby the opacifying agent, distributed as a component of the processingcomposition,

intermediate the reception layer and next adjacent silver halideemulsion layer. The thus-formed opacifying stratum effectively masksresidual dye image-providing material retained in association with thesilver halide emulsion layer subsequent to processing.

As disclosed in the copending US. patent application Ser. No. 846,441 ofEdwin H. Land, filed July 31, 1969 now US. Pat. No. 3,615,421 and thecopending US. patent application Ser. No. 3,646 of Sheldon A. Buckler,filed Jan. 19, 1970 and now U.S. Pat. No. 3,661,585, the opacifyingcomponent of the film unit may optionally be initially disposed as apreformed processing composition permeable layer, intermediate thereception layer and next adjacent silver halide layer, in aconcentration which prior to photoexposure is insufficient to preventtransmission therethrough of exposing actinic radiation and which,subsequent to processing, possesses an opacifying capacity effective tomask residual dye image-providing material retained associated with thefilm units silver halide emulsion layers.

In the copending US. patent application Ser. No. 786,352 of Edwin H.Land, filed Dec. 23, 1968, the opacifying component is disclosed tooptionally comprise a light-absorbing reagent such as a dye which ispresent as an absorbing species at the first pH and which may beconverted to a substantially nonabsorbing species at the second pH.

In US. Pat. No. 3,573,043 of Edwin H. Land, issued Mar. 30, 1971, thepolymeric neutralizing layer is disclosed to be optionally disposedintermediate the dimensionally stable opaque layer and next adjacentessential layer, i.e., next adjacent silver halide/dye image-providingmaterial component, to effect the designated modulation of film unitsenvironmental pH, and the US. Pat. No. 3,576,625 of Edwin H. Land,issued April 27, 1971, discloses the employment of particulate aciddistributed within the film unit to effect the modulation of theenvironmental pH.

Copending application Ser. No. 43,782 filed June 5, 1970, now abandoned,discloses and claims an improved film unit assemblage of theaforementioned general structural parameters and adapted to beprocessed, subsequent to photoexposure, in the presence of actinicradiation will be fabricated to employ, as the opacifying meansinterposed intermediate the receptive layer and next adjacent silverhalide layer subsequent to photoexposure, an inorganic light-refiectingpigment dispersion containing refiecting pigment dispersion in aconcentration per se insufficient, distributed as a layer intermediatethe receptive layer and next adjacent silver halide layer, toeffectively prevent transmission of radiation actinic to the silverhalide layer therethrough and at least one optical filtering agent, at apH above the pK of the optical filter agent, in a concentration also perse insufficient to prevent transmission of actinic radiationtherethrough, which concentrations individually and additively aretogether insufficient to prevent transmission of incident actinicradiation, but in admixture are synergistically effective to provide abarrier to such transmission. Thus, the optical filter agent isempirically effective in combination with the pigment to preventtransmission of radiation actinic to the silver halide layers incidenton the layer comprising the dispersion, during processing in thepresence of actinic radiation, and sufficiently low to providesubstantially immediate viewing of transfer image formation against thebackground provided by the reflecting pigment. Such effective minimalconcentration of filter agent specifically facilitates the accelerationof the clearing time involved in discharging from visual observation thefilter agent employed by reduction of the environmental pH as detailedabove from above to below the K of the filter agent selected.

SUMMARY OF THE INVENTION The present invention is directed to a new andimproved integral negative/positive diffusion transfer processphotographic film unit adapted to provide, by diffusion transferprocessing, a reflecting print photographic image reproduction as afunction of exposure of such film unit to incident actinic radiation.

The film unit assemblage construction to be employed in the practice ofthe present invention comprises a film unit of the general type setforth above, e.g., in the aforementioned U.S. Pats. Nos. 3,415,644;3,573,043; 3,576,- 625; and 3,615,421 and 3,586,501 and copendingapplication Ser. No. 786,352, and may comprise, in essence, a compositephotosensitive element which includes a plurality of layers includingone or more photosensitive silver halide layers having associatedtherewith image-forming material which is processing compositiondiffusible as a function of the point-to-point degree of silver halidelayer exposure to incident actinic radiation; a layer adapted to receiveimage-forming material diffusing thereto; means for interposing, atleast one optical filter agent; and means for modulating the pH of thefilm unit step-wise in at least two pH increments.

A particularly preferred film assemblage of the present inventioncomprises, in essence, a composite photosensitive element which includesa plurality of layers including, in relative order, a dimensionallystable layer opaque to incident actinic radiation; one or morephotosensitive silver halide layers having associated therewithimageforming material which is processing composition diffusible as afunction of the point-to-point degree of silver halide layer exposure toincident actinic radiation; :1 layer adapted to receive image-formingmaterial diffusing thereto; means for interposing, intermediate thesilver halide layers and the reception layer, an inorganic reflectingpigment dispersion containing at least one optical filter agent; andmeans for modulating the pH of the film unit stepwise in at least two pHincrements.

In accordance with the present invention, it has been quite unexpectedlydiscovered that an improved film unit assemblage of the aforementionedgeneral structural parameters and adapted to be processed, subsequent tophotoexposure, in the presence of actinic radiation will be fabricatedto employ, as the opacifying means interposed intermediate the receptionlayer and next adjacent silver halide layer subsequent to photoexposure,an inorganic light-reflecting pigment and at least one optical filteragent, the concentrations of which individually and additively aretogether insufficient to prevent transmission of incident actinicradiation but in admixture are synergistically effective to provide abarrier to such transmission, which film assemblage also contains meansfor modulating the pH of the system from a first pH wherein the dyeimage-forming material is diffusible; said first pH being above the pK,,of the optical filter element, to a second pH wherein the optical filterelement is rendered substantially ineffective as a light-absorbingbarrier, said second pH being below the pK of said optical filterelement, but at which pH said dye image-forming material is stilldifiusible, to a third pH at which the dye image-forming material issubstantially nondiffusible.

Thus, subsequent to exposure of the photosensitive element anddistribution of the aqueous alkaline processing composition andopacifying means intermediate the reception layer and next adjacentsilver halide layer, the first pH of the system, as provided by theaqueous alkaline composition, initiates development and the forming ofan imagewise distribution of mobile dye image-forming material as afunction of the point-to-point degree of emulsion exposure. Subsequentto the diffusion of said dye image-forming material from its initialposition in the element, i.e., at a point wherein the mobility of thedye image-forming material has been modulated by the exposed silverhalide, the pH of the system is adjusted to a second pH wherein theoptical filter agent is substantially ineffective as a light-absorbingbarrier; said dye imageforming material being dilfusible at said secondpH. Subsequent to substantial dye transfer image formation, the

pH of the system is reduced to a third pH wherein said dye image-formingmaterial is substantially nondilfusible.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of aphotographic film unit embodying the invention;

FIGS. 2, 4 and 6 are diagrammatic enlarged crosssectional views of thefilm unit of FIG. 1, along section line 2-2, illustrating theassociation of elements during the three illustrated stages of theperformance of a diffusion transfer process, for the production of amulticolor transfer image according to the invention, the thickness ofthe various materials being exaggerated, and wherein FIG. 2 representsan exposure stage, FIG. 4 represents a processing stage and FIG. 6represents a product of the process; and

FIGS. 3, and 7 are diagrammatic, further enlarged cross-sectional viewsof the film unit of FIGS. 2, 4 and 6, along section lines 33, 55 and7-7, respectively, further illustrating, in detail, the arrangement oflayers comprising the photosensitive laminate during the threeillustrated stages of the ransfer process.

DETAILED DESCRIPTION OF THE INVENTION As previously characterized,diffusion transfer photographic processing may be employed to provide apositive reflection image, as a direct function of actinic radiationincident on a film unit assemblage specifically constructed to comprise,in essence, a plurality of sequential layers including a layer opaque toincident actinic radiation; a photosensitive silver halide layer havingassociated therewith image-forming material and preferably dyeimageforming material which is processing composition diffusible as afunction of the point-to-point degree of silver halide layerphotoexposure; and a layer adapted to receive image-forming materialdiffusing thereto; wherein the assemblage additionally contains meansfor interposing, intermediate the silver halide layer and the receptionlayer, an inorganic reflecting pigment and at least one optical filteragent, at a pH above the pK of the filter agent, in a concentrationeffective to provide a light-absorbing barrier between the receptionlayer and silver halide layer, and means for converting the pH of thedispersion from a pH above the pK of the optical filter agent to asecond pH below the pK,, of the optical filter agent, whereby theexposure protection is discharged, but at which second pH thediffusibility of the dye image-forming material is not impaired; andmeans providing for converting said second pH to a third pH at whichsaid dye image-forming material is nondiflusible.

In a particularly preferred embodiment, the aforementioned inorganicreflecting pigment and optical light filter agent as employed in aconcentration which provides, at a pH above the pK of the filter agent,a layer exhibiting optical transmission density -6.() density units andoptical reflection density -l.0 density units subsequent tophotoexposure of the silver halide layer.

It has been found that the film unit assemblage constructed inaccordance with the present invention is specifically adapted forprocessing in the presence of actinic radiation by reason of theprotection afforded the silver halide layers exposure surface by thepresence of the pigment and filter agent protecting from exposure suchsurface, and for the simultaneous viewing of the transfer image carriedby the reception layer by reason of the minimal optical reflectiondensity exhibited by the lightreflecting pigment layer, subsequent tophotoexposure of the silver halide layer and in situ formation of thepigment layer. There is thus provided by means of the present inventionsubstantially immediate viewing of transfer image formation against areflecting pigment layer background exhibiting substantially nocontamination from the optical reflecting agent employed with thepigment layer to prevent transmission of fog producting actinicradiation through the reflecting layer and thus protecting the silverhalide layer during initial stages of transfer processing, i.e., duringthat period of time required for the silver halide to modulate themobility of the dye imageproviding material. The de minimusconcentration of optical filter agent discovered to be capable ofeffective employment to prevent light transmission when dispersed inintimate relationship with reflecting pigment optimizes discharge of thereflectivity provided by the agent upon decrease of the environmental pHat which the optical filter agent absorbs radiation to that pH at whichsuch agent is substantially innocuous optically, but at whichdiffusibility of the dye image-forming materials is unimpaired.

It should be understood that reference to modulating the pH of the filmunit or system is intended to refer to a pH change in at least thoseareas of the film unit where the optical filter agent and/orimage-forming material is located.

The preferred means for modulating the pH of the system from a first pHwherein the dye image-forming materials are ditfusible and the opticalfilter agent is operative with the inorganic reflecting pigment toprovide the above mentioned barrier to actinic radiation, to a second pHwherein the image-forming materials are diffusible but which second pHis below the pK,, of the optical filter agent and which thus dischargesthe light-absorbing barrier, are non-volatile acids. Any suitable acidmay be employed, including high or low molecular weight acids; they maybe introduced into the photographic film unit as molecular dispersions,solid dispersions, emulsions or solutions.

The acidic additive may be disposed in any convenient location in thefilm 'unit provided it is made available to accomplish theaforementioned clearing of the optical filter agent without adverselyeffecting the image-forming process or deleteriously effecting thephotographic quality of the system. Thus, the acidic additive may bedisposed in the photosensitive element, in the image-receiving layer orin a separate layer disposed adjacent either of said layers. Because ofthe variety of materials suitable for use, and the properties and formsavailable, the acidic additive can be disposed in a variety of locationsand formats to provide the necessary time delay to permit appreciablediffusion of dye image-forming materials and then obtain the relativelyprecipitous drop of the pH of the system to a point below the pK,, ofthe optical filter agent. Thus, the time delay may be effected byspatially removing the acidic additive from the locus of the opticalfilter agent or by locating the acidic additive relatively close to theoptical filter agent but providing said acidic additive in such aspecies that will provide the required time delay.

In a particularly preferred embodiment, the acidicadditive is disposedin the layer adapted to receive the imageforming material.

The term acidic additive is intended to include acids and compoundsadapted to provide an acidic moiety in the system. It is necessary,however, that the K of the acidic additive be below that of theparticular optical filter agent employed.

As examples of suitable acidic additives, mention may be made of thefollowing:

benzoic acid methane sulfonamide benzyl malonic acid phthalic acidfumaric acid p-toluene sulfonamide N-methyl-p-toluene sulfonamideN-ethyl-p-toluene sulfonamide citric acid d-tartaric acid sulfanilarnidesalicylic acid 5-sulfosalicylic acid sulfoacetic acid benzenesulfonamide methane sulfonamide 2-toluene sulfonic acid In analternative embodiment, an acid salt of a conventional antifoggant isemployed, preferably in the layer adapted to receive the image-formingmaterials, to provide antifoggant activity and the means for reducingthe initial pH to a second pH. As examples of such antifoggants, mentionmay be made of acid salts of benzotriazole and benzimidazole.

In an alternative embodiment, the film element includes buffering meansto maintain said second pH wherein the optical filter element isrendered substantially ineffective as a light-absorbing barrier, atwhich pH the dye imageforming material is still ditfusible, for a timesufficient to permit substantial dye image-forming material transfer.

In other words, a plot of pH versus time would show a curve indicatingpH decrease to a point below the PK of the optical filter elementwhereupon it would plateau while transfer of image-forming materialproceeded and then again indicate pH drop to a point where saidimageforming material is substantially non-diffusible.

The particular compound employed as the buffering means is selected withrespect to the specific pK desired, i.e., with respect to the specificoptical filter element employed and the period of time during whichbuffering would occur. Preferably, a compound of relatively high pK isemployed. More preferably, the compounds are acid salts or acids whichwill form salts with the aqueous alkaline processing composition. Whendisposed in the processing composition, the compound must also be stablein alkali and not degrade in storage. It must also not deleteriouslyinterfere with the photographic operation of the film unit.

The compound to provide the buffering means may be disposed in anyconvenient location in the film unit provided it is made available toaccomplish the aforementioned buffering of the processing compositionwithout adversely effecting the image-forming process or deleteriouslyeffecting the photographic quality of the system. Thus, the compound maybe disposed in the photosensitive element, in the image-receiving layeror in a separate layer disposed adjacent either of said layers or in thecontainer with the processing composition.

In a particularly preferred embodiment, the compound to providebuffering means is disposed in the processing composition.

As examples of suitable compounds, mention may be made of the following:

sodium ortho silicate sodium meta silicate potassium meta silicatep-toluene sulfonamide salts of salicylic acid salts of phosphoric acidfumed silica salts of ethylenediamine tetraacetic acid benzenesulfonamide N-methyl-p-toluene sulfonamide N-ethyl-p-toluene sulfonamidesulfonilamide methane sulfonamide It will be recognized that it isnecessary to prevent the diffusion to the image-receiving layer ofadditional dye image-forming material resulting from the exposure ofsilver halide after discharge of the light absorbing barrier. If thetime delay between the discharge of the lightabsorbing barrier and themodulation of the pH of the system, wherein the dye image-formingmaterials are nondiffusing, is sufficiently long, it is not necessary toprevent transfer of dye image-forming materials or to render the silverhalide nondevelopable since the mobility of the dye image-formingmaterials would not permit said materials to reach the dyeable layer inthe given time sequence before the pH reduction rendered all componentsin the film unit immobile.

Alternatively, means may be employed to cause the developable silverhalide to remain undeveloped. It has been found that such control may beaccomplished by incorporating in a layer of either the photosensitiveelement or the image-receiving element, or in some instances in theprocessing composition, a reagent which is made available to thedevelopable silver halide of a given emulsion layer only after apredetermined period during which development is effected withoutinterference by said reagent. Since this added reagent effectivelyrestrains, i.e., minimizes, further development of developable silverhalide after this predetermined period, suitable reagents employed forthis purpose may be referred to as development restrainers. While suchreagents frequently will have characteristics similar to reagentscommonly referred to as antifoggants", they perform a function hereindifferent from what is normally contemplated as the function of anantifoggant, i.e. their function is not to reduce the fog density inunexposed areas, although under some circumstances, they may alsoperform this function to a small degree. In some instances, a givenreagent may be used in a small concentration in the processingcomposition wherein it functions as an antifoggant, and an additionalquantity is contained in the photosensitive element or in theimagereceiving element in a form whereby it is released only after apredetermined period whereupon it acts as a development restrainer.

Reagents which are particularly suitable for use as developmentrestrainers are those which will form products or complexes withundeveloped silver halide, whether exposed or unexposed, but at leastwith exposed silver halide, which products or complexes aresubstantially less developable by a silver halide developing agent,e.g., by the dye developer, and which preferably are substantiallyinsoluble, and hence essentially undevelopable, i.e. developable onlywith difficulty. In a preferred embodiment, the desired predeterminedperiod during which development is effected without interference isaccomplished by incorporating the development restrainer in a chemicalform or in a physicial location such that its availability to thedevelopable silver halide is limited or restricted, e.g., as a result ofthe distance through which it must diffuse to reach the developingsilver halide, or as a consequence of a significantly lower diffusionrate than said developing agents. Where the development restrainer is atleast initially substantially slower in diffusion than the dyedeveloper, as for example, as a result of the inclusion of a relativelylong chain alkyl group, the development restrainer may be positioned ina layer of the multilayer negative, e.g., in the dye layer containingthe dye developer or in an interlayer positioned on the side of the dyelayer remote from the silver halide emulsion layer. A relatively morediffusible development restrainer may be used provided that it islocated sufficiently remote physically from the silver halide emulsionlayer upon which it is to act, as by incorporation in the imagereceivinglayer, i.e., in the image-receiving layer itself or in a layer over theimage-receiving layer or in a subcoat beneath the image-receiving layer.Such development restrainers may also be incorporated in a layer in thephotosensitive element provided said restrainer is present in such aform as to be only slowly dissolved by the processing composition. Undersome circumstances, the development restrainer may be similarlycontained in a coating over the outermost or blue-sensitive silverhalide emulsion layer.

Development restrainers suitable for use in the processes of thisinvention will readily suggest themselves to one skilled in the art. Byway of illustration, mention may be made of long chain thiobarbituricacids, e.g., dodecyl 9 thiobarbituric acid, andphenyl-mercaptotetrazoles, e.g., 1- phenyl-S-mercaptotetrazole.

In a preferred embodiment of the invention, the development restrainersare employed, in combination, with an antifoggant initially contained inthe processing composition and/or in a layer of the photosensitiveelement so as to be available for action relatively promptly after theapplication of the processing composition. Such antifoggants perform theusual function of an antifoggant, i.e., they minimize the development ofsilver fog in unexposed and partially exposed areas of the severalphotosensitive silver halide emulsions and increase the differentiationbetween exposed and unexposed silver halide by the developing agent. Aspreviously noted, the development restrainer may and frequently is acompound of the broad class of reagents frequently referred to asantifoggants. An essential distinction between the use of a compound asan antifoggant and as a development restrainer as contemplated by thisinvention is in the time sequence in which it is available to act uponthe silver halide emulsion layer. Furthermore, many useful developmentrestrainers may be found among compounds whose action upon silver halideis too vigorous to be effectively employed as antifoggants, since theywould tend to reduce density in the areas-intended to be developed.Since it is the purpose of the development restrainers in the instantinvention to render the residual developable silver halide substantiallyundevelopable after a predetermined period of development, we maysuccessfully use a reagent which acts nonimagewise in rendering theremaining undeveloped silver halide, exposed and unexposed,undevelopable by the silver halide developing agent or agents present.

In a particularly preferred embodiment, the film unit includes acompound which is a precursor of the desired development restrainerwhich is capable of releasing the active species of the compound at atemperature dependent rate. Antifoggant precursors are described andclaimed in US. Pat. No. 3,575,699 issued Apr. 20, 1971.

In still another alternative embodiment, control of the silver halidemay be accomplished by providing means for desensitizing the silverhalide, thus rendering it innocuous with respect to providing additionaldiffusible image-providing material. Conventional desensitizers known tothe art may be provided associated with the photosensitive element andadapted to be released substantially contemporaneous with the dischargeof the light-absorbing barrier.

Multicolor images may be obtained using color imageforming components inthe diffusion transfer process of the present invention by severaltechniques. One such technique contemplates obtaining multicolortransfer images utilizing, for example, dye developers as dyeimage-providing materials by employment of an integral multilayerphotosensitive element, such as is disclosed in the aforementioned US.Pat. No. 3,415,644 wherein at least two selectively sensitizedphotosensitive -strata, superposed on a single support, are processed,simultaneously and without separation, with a single, commonimagereceiving layer. A suitable arrangement of this type comprises theopaque support carrying a red-sensitive silver halide stratum, agreen-sensitive silver halide stratum and a blue-sensitive silver halidestratum, said emulsions having associated therewith, respectively, forexample, a cyan dye developer, a magenta dye developer and a yellow dyedeveloper. The dye developer may be utilized in the silver halidestratum, for example, in the form of particles, or it may be employed asa layer behind the appropriate silver halide strata. Each set of silverhalide strata and associated dye developer strata are disclosed to beoptionally separated from other sets by suitable interlayers, forexample, by a layer of gelatin or polyvinyl alcohol. In certaininstances, it may be desirable to incorporate a yellow filter in frontof the green-sensitive emulsion and such yellow filter may beincorporated in an inter-layer. However, where desirable, a yellow dye10 developer of the appropriate spectral characteristics and present ina state capable of functioning as a yellow filter may be employed. Insuch instances, a separate yellow filter may be omitted.

In a preferred embodiment of the present invention, the film unit isspecifically adapted to provide for the production of a multicolor dyetransfer image and the photosensitive laminate comprises, in order ofessential layers, the dimensionally stable opaque layer; at least twoselectively sensitized silver halide strata each having dyeimage-providing material of predetermined color associated therewith,for example, dye developers as detailed above, which are soluble anddiffusible in processing composition as a function of the point-to-pointdegree of exposure of the respective associated silver halide strata; apolymeric layer dyeable by the dye image-providing materials; and adimensionally stable transparent layer.

In view of the fact that the preferred dye image-providing materialscomprise dyes which are silver halide developing agents, as statedabove, for purposes of simplicity and clarity, the present inventionwill be further described hereinafter in terms of such dyes, withoutlimitation of the invention to the illustrative dyes denoted, and, inaddition the photographic film unit structure will be detailedhereinafter employing the last-mentioned preferred structuralembodiment, without limitation of the invention to the preferredstructure denoted.

The dye developers, as noted above, are compounds which contain, in thesame molecule, both the chromophoric system of a dye and also a silverhalide developing function. By a silver halide developing function ismeant a grouping adapted to develop exposed silver halide. A preferredsilver halide development function is a hydroquinonyl group. Othersuitable developing functions include ortho-dihydroxyphenyl and orthoandparaamino substituted hydroxyphenyl groups. In general, the developmentfunction includes a benzenoid developing function, that is, an aromaticdeveloping group which forms quinonoid or quinone substances whenoxidized.

The dye developers are preferably selected for their ability to providecolors that are useful in carrying out substractive color photography,that is, the previously mentioned cyan, magenta and yellow. The dyedevelopers employed may be incorporated in the respective silver halideemulsion or, in the preferred embodiment, in a separate layer behind therespective silver halide stratum. Specifically, the dye developer may,for example, be in a coating or layer behind the respective silverhalide stratum and such a layer of dye developer may be applied by useof a coating solution containing about 0.5 to 8%, by weight, of therespective dye developer distributed in a film-forming natural, orsynthetic, polymer, for example, gelatin, polyvinyl alcohol, and thelike, adapted to be permeated by the chosen diffusion transfer fluidprocessing composition.

The silver halide strata comprising the multicolor photosensitivelaminate preferably possess predominant spectral sensitivity to separateregions of the spectrum and each has associated therewith a dye which isa silver halide developing agent and is, most preferably, substantiallysoluble in the reduced form only at a first pH pos sessing, subsequentto processing, a spectral absorption range substantially complementaryto the predominant sensitivity range of its associated emulsion.

In the preferred embodiment, each of the silver halide strata, and itsassociated dye, is separated from the remaining strata, and theirassociated dye, by separate alkaline solution permeable polymericinterlayers.

In such preferred embodiment of the invention, the silver halide stratumcomprise photosensitive silver halide dispersed in gelatin and are about0.6 to 6 microns in thickness; the dye itself is dispersed in an aqueousalkaline solution polymeric binder, preferably gelatin, as a separatelayer about 1 to 7 microns in thickness; the alkaline solution permeablepolymeric interlayers, preferably gelatin, are about 1 to microns inthickness; the dyeable polymeric layer is transparent and about 0.25 to0.4 mil in thickness; and each of the dimensionally stable opaque andtransparent layers are alkaline solution impermeable, processingcomposition vapor permeable and about 2 to 6 mils in thickness. It wilbe specifically recognized that the relative dimensions recited abovemay be appropriately modified, in accordance with the desires of theoperator, with respect to the specific product to be ultimatelyprepared.

In the preferred embodiment of the present inventions film unit for theproduction of a multicolor transfer image, the respective silverhalide/dye developer units of the photosensitive element will be in theform of a tripack configuration which will ordinarily comprise a cyandye developer/red-sensitive emulsion unit contiguous the dimensionallystable opaque layer, the yellow dye developer/blue-sensitive emulsionunit most distant from the opaque layer and the magenta dyedeveloper/greensensitive emulsion unit intermediate those units,recognizing that the relative order of such units may be varied inaccordance with the desires of the operator.

Reference is now made to FIGS. 1 through 7 of the drawings wherein thereis illustrated a preferred film unit of the present invention andwherein like numbers, appearing in the various figures, refer to likecomponents.

As illustrated in the drawings, FIG. 1 sets forth a perspective view ofthe film unit, designated 10, and each of FIGS. 2 through 7 illustratediagrammatic cross-sectional views of film unit 10, along the statedsection lines 2--2, 3-3, 5-5 and 77, during the various depicted stagesin the performance of a photographic diffusion transfer process asdetailed hereinafter.

Film unit 10 comprises rupturable container 11, retaining, prior toprocessing, aqueous processing composition 12, and photosensitivelaminate 13 including, in order, dimensionally stable opaque layer 14,preferably an actinic radiation-opaque flexible sheet material; cyan dyedeveloper layer 15; red-sensitive silver halide emulsion layer 16;interlayer 17; magenta dye developer layer 18; greensensitive silverhalide emulsion layer 19; interlayer 20; yellow dye developer layer 21;blue-sensitive silver halide emulsion layer 22; auxiliary layer 23,which may contain an auxiliary silver halide developing agent;image-receiving layer 24; spacer layer 25; neutralizing layer 26; anddimensionally stable transparent layer 27, preferably an actinicradiation transmissive flexible sheet material.

The structural integrity of laminate 13 may be maintained, at least inpart, by the adhesive capacity exhibited between the various layerscomprising the laminate at their opposed surfaces. However, the adhesivecapacity exhibited at an interface intermediate image-receiving layer 24and the silver halide emulsion layer next adjacent thereto, for example,image-receiving layer24 and auxiliary layer 23 as illustrated in FIGS. 2through 7, should be less than that exhibited at the interface betweenthe opposed surfaces of the remainder of the layers forming thelaminate, in order to facilitate distribution of processing solution 12intermediate the stated image-receiving layer 24 and the silver halideemulsion layer next adjacent thereto. The laminates structural integritymay also be enhanced or provided, in whole or in part, by providing abinding member extending around, for example, the edges of laminate 13,and maintaining the layers comprising the laminate intact, except at theinterface between layers 23 and 24 during distribution of processingcomposition 12 intermediate those layers. As illustrated in the figures,the binding member may comprise a pressure-sensitive tape 28 securingand/or maintaining the layers of laminate 13 together at its respectiveedges. Tape 28 will also act to maintain processing solution 12intermediate imagereceiving layer 24 and the silver halide emulsionlayer next adjacent thereto, upon application of compressive pressure topod 11 and distribution of its contents intermediate the stated layers.Under such circumstances,

12 binder tape 28 will act to prevent leakage of fluid processingcomposition from the film units laminate during and subsequent tophotographic processing.

Rupturable container 11 may be of the type shown and described in any ofUS. Pats. Nos. 2,543,181; 2,634,886; 3,653,732; 2,723,051; 3,056,492;3,056,491; 3,152,515; and the like. In general, such containers willcomprise a rectangular blank of fluidand air-impervious sheet materialfolded longitudinally upon itself to form two walls 29 which are sealedto one another along their longitudinal and end margins to form a cavityin which processing composition 12 is retained. The longitudinalmarginal seal 30 is made weaker than the end seals 31 so as to becomeunsealed in response to the hydraulic pressure generated within thefluid contents 12 of the container by the application of compressivepressure to walls 29 of the container.

As illustrated in FIGS. 1, 2 and 3, container 11 is fixedly positionedand extends transverse a leading edge of photosensitive laminate 13whereby to efifect unidirectional discharge of the containers contents12 between image-reeeiving layer 24 and the stated layer next adjacentthereto, upon application of compressive force to container 11. Thus,container 11, as illustrated in FIG. 2, is fixedly positioned andextends transverse a leading edge of laminate 13 with its longitudinalmarginal seal 30 directed toward the interface between image-receivinglayer 24 and auxiliary layer 23. As shown in FIGS. 1, 2 and 4, container11 is fixedly secured to laminate 13 by extension 32 of tape 28extending over a portion of one wall 29 of the container, in combinationwith a separate retaining member such as illustrated retaining tape 33extending over a portion of laminate 13s surface generally equal in areato about that covered by tape 28.

As illustrated in FIG. 6, extension flap 32 of tape 28 is preferably ofsuch area and dimensions that upon, for example, manual separation ofcontainer 11 and tape 33, subsequent to distribution of processingcomposition 12, from the remainder of film unit 10, flap 32 may befolded over the edge of laminate 13, previously covered by tape 33, inorder to facilitate maintenance of the laminates structural integrity,for example, during the flexations inevitable in storage and use of theprocessed film unit, and to provide a suitable mask or frame, forviewing of the transfer image through the picture viewing area oftransparent layer 27.

The fluid contents of the container comprise an aqueous alkalinesolution having a pH and solvent concentration at which the dyedevelopers are soluble and diffusible and contains inorganiclight-reflecting pigment and at least one optical filter agent at a pHabove the pK of such agent in a quantity sufficient, upon distribution,effective to provide a light-absorbing barrier, preferably a layerexhibiting optical transmission density -6.0 and optical reflectiondensity -l.0 to prevent exposure of photosensitive silver halideemulsion layers 16, 19 and 22 by actinic radiation incident ondimensionally stable transparent layer 27 during processing in thepresence of such radiation and to afford immediate viewing of dye imageformation in image-receiving layer 24 during and subsequent to dyetransfer image formation. Accordingly, the film unit may be processed,subsequent to distribution of the composition, in the presence of suchradiation, in view of the fact that the silver halide emulsion oremulsions of laminate are appropriately protected by incident radiation,at one major surface of the opaque processing composition and at theremaining major surface by the dimensionally stable opaque layer. If theillustrated binder tapes are also opaque, edge leakage of actinicradiation incident on the emulsion or emulsions will also be prevented.

The selected reflecting pigment should be one providing a backgroundsuitable for viewing the dye developer transfer image formed in thedyeable polymeric layer. In general, while substantially any reflectingagent may be employed, it is preferred that a reflecting agent beselected that will not interfere with the color integrity of the dyetransfer image, as viewed by the observer, and, most preferably, anagent which is aesthetically pleasing to the viewer and does not providea background noise signal degrading, or detracting from, the informationcontent of the image. Particularly desirable reflecting agents will bethose providing a white background, for viewing the transfer image, andspecifically those conventionally employed to provide background forreflection photographic prints and, especially those agents possessingthe optical properties desired for reflection of incident radiation.

As examples of reflecting pigments adapted for employment in thepractice of the present invention, mention may be made of bariumsulfate, zinc sulfide, titanium dioxide, barium stearate, silver flake,silicates, alumina, zirconium oxide, zirconium acetyl acetate, sodiumzirconium sulfate, kaolin, mica, and the like.

A particularly preferred reflecting agent comprises titanium dioxide dueto its highly effective reflection properties. In general, in suchpreferred embodiment, based upon percent titanium dioxide(weight/volume) a processing composition containing about 1500 to 4000mgs./ ft. titanium dioxide dispersed in 100 cc. of water will provide apercent reflectance of about 85 to 90%. In the most preferredembodiments, the percent reflectance particularly desired will be in theorder of -85 In embodiments wherein the dispersion comprises a preformedlayer positioned intermediate the reception layer and next adjacentsilver halide layer, the pigment layer will be sufficiently transparentto allow transit of exposing radiation through the pigment layer and maycomprise titanium dioxide reflecting agent possessing a particle sizedistribution averaging -0.2 micron in diameter and preferably -0.05micron in diameter as initially present preceding exposure of the filmunit, which preferred materials, upon contact with aqueous alkalineprocessing composition, preferably aggregate to provide particlespossessing a diameter in excess of -0.2 micron in diameter and will becoated at a coverage of -200 to 1000 mgs./ft. Specifically, thereflecting agent will be present in a quantity insufficient to preventexposure of the emulsion layers by actinic radiation incident on thedimensionally stable transparent layer of the film unit but in aconcentration sufficient, subsequent to processing, to mask dyedeveloper associated with the silver halide emulsion strata from the dyetransfer image. In the preferred construction of such embodiment, thepigment such as titanium dioxide will be initially present in arelatively small particle size to provide unexpectedly efficient transitof radiation through the reflecting layer during exposure which uponcontact with an alkaline processing composition and aggregation of thepigment particles provides eificient light reflectivity and maskingcapacity subsequent to such aggregation.

In general, the reflecting agents to be employed are those which remainsubstantially immobile within their respective compositions during andsubsequent to photographic processing and particularly those whichcomprise insoluble and nonditfusible inorganic pigment dispersionswithin the layer in which they'are disposed.

Where desired, reflecting agent pigment may thus be distributed in wholeor in part within a processing composition permeable polymeric matrixsuch as gelatin and/ or any other such polymeric matrixes as arespecifically denoted throughout the specification as suitable foremployment as a matrix binder and may be distributed in one or more ofthe film unit layers which may be separated or contiguous, intermediatethe image-receiving layer and next adjacent silver halide layer,provided that its distribution and concentration is effective to providethe denoted post processing masking function, and/ or in whole or inpart the reflecting agent may be ultimately disposed within theprocessing composition 14 residuum located intermediate theimage-receiving layer and next adjacent silver halide emulsion strataand associated dye image-forming material.

The optical filter agent selected should be one exhibiting, at a pHabove its pK,,, maximum spectral absorption of radiation at thewavelengths to which the film units photosensitive silver halide layeror layers are sensitive and should be substantially immobile ornonditfusible Within the pigment dispersion, during performance of itsradiation filtration function, in order to maintain and enhance theoptical integrity of the dispersion as a radiation filter unitfunctioning in accordance with the present invention, and to prevent itsdiffusion into and localized concentration within the image-receivinglayer thereby decreasing the efficiency of the reflecting pigmentdispersion as a background against which image formation may beimmediately viewed, during the initial stages in the diffusion transferprocessing of the film unit, by filter agent absorption of dispersionreflected visible radiation prior to reduction in the environmental pHbelow the pK of the agent. Commensurate with the spectral sensitivityrange of the associated silver halide layer or layers, the opticalfilter agent selected may comprise one or more filter dyes possessingabsorption complementary to such silver halide layers in order toprovide effective protection against physical fog providing radiationduring processing. Recognizing that the filter agent absorption willderogate from image-viewing characteristics by contaminating reflectingpigment background, the selected agents must be those exhibiting majorspectral absorption at the pH at which processing is effected andminimal absorption at a pH below that which obtains during transferimage formation. Accordingly, the selected optical filter agent oragents must possess a pK below that of the processing pH and above thatof the environmental pH subsequent to transfer image formation, and willbe selected for employment in the minimum concentration necessary toprovide an optical transmission density -6.0, at wavelengths at whichthe silver halide layer is maximally responsive, and in no instance anoptical reflection density -1.0 at such wavelengths.

As examples of such pH-sensitive optical filter agents adapted foremployment in the practice of the present invention, mention may be madeof:

N N H H H 0011 C O OH 11-C18H370 Co OH HO OH HO OH C O OH (26) HO OH SOzNH CH7 CH3- NH-S O2 n-CizHzs W C1z 2a- O OH In general, preferredagents, both opacifying and filter, are those which remain immobileWithin their respective compositions during and subsequent tophotographic processing and particularly those which comprise insolubleand nondiifusible materials.

As disclosed in the previously cited patents, the liquid processingcomposition referred to for effecting multicolor diffusion transferprocesses comprises at least an aqueous solution of an alkalinematerial, for example, diethylamine, sodium hydroxide or sodiumcarbonate and the like, and preferably possessing a pH in excess of 12,and most preferably includes a viscosity-increasing compoundconstituting a film-forming material of the type which, when thecomposition is spread and dried, forms a relatively firm and relativelystable film. The preferred film-forming materials disclosed comprisehigh molecular weight polymers such as polymeric, water-soluble etherswhich are inert to an alkaline solution such as, for example, ahydroxyethyl cellulose or sodium carboxymethyl cellulose. Additionally,film-forming materials or thickening agents whose ability to increaseviscosity is substantially unaffected if left in solution for a longperiod of time are also disclosed to be capable of utilization. Asstated, the film-forming material is preferably contained in theprocessing composition in such suitable quantities as to impart to thecomposition a viscosity in excess of c.p.s. at a temperature ofapproximately 24 C. and preferably in the order of 100,000 c.p.s. to200,000 c.p.s. at that temperature.

In the performance of a dilfusion transfer multicolor process employingfilm unit 10, the unit is exposed to radiation, actinic tophotosensitive laminate 13, incident on the laminates exposure surface34, as illustrated in FIG. 2.

Subsequent to exposure, as illustrated by FIGS. 2 and 4, film unit 10 isprocessed by being passed through opposed suitably gapped rolls 35 inorder to apply compressive pressure to frangible container 11 and toeffect rupture of longitudinal seal 30 and distribution of alkalineprocessing composition 12, possessing inorganic light-reflecting pigmentand optical filter agent at a pH above the pK of the filter agent and apH at which the cyan, magenta and yellow dye developers are soluble anddifiusible as a function of the point-to-point degree of exposure ofred-sensitive silver halide emulsion layer 16, green-sensitive silverhalide emulsion layer 19 and blue-sensitive silver halide emulsion layer22, respectively, intermediate reflecting agent precursor layer 25 andauxiliary layer 23.

Alkaline processing composition 12 permeates emulsion layers 16, 19 and22 to initiate development of the latent images contained in therespective emulsions. The cyan, magenta and yellow dye developers, oflayers 15, 18 and 21, are immobilized, as a function of the developmentof their respective associated silver halide emulsions, preferablysubstantially as a result of their conversion from the reduced form totheir relatively insoluble and nondiffusible oxidized form, therebyproviding imagewise distributions of mobile, soluble and dilfusiblecyan, magenta and yellow dye developer, as a function of thepoint-topoint degree of their associated emulsions exposure. At leastpart of the imagewise distributions of mobile cyan, magenta and yellowdye developer transfers, by dilfusion, to dyeable polymeric layer 24 toprovide a multicolor dye transfer image to that layer which is viewableagainst the background provided by the reflecting pigment present inprocessing composition residuum 12 and cyan, magenta and yellow dyedeveloper remaining associated with bluesensitive emulsion layer 22,green-sensitive emulsion layer 19 and red-sensitive emulsion layer 16.Subsequent to substantial transfer image formation, a sulficient portionof the ions comprising aqueous alkaline processing composition 12transfer, by diffusion, through permeable polymeric reception layer 24,permeable spacer layer 25 to polymeric neutralizing layer 26 whereby theenvironmental pH of the system decreases as a function of neutralizationto a pH at which the cyan, magenta and yellow dye developers, in thereduced form, are substantially nondiflusible to thereby provide astable multicolor dye transfer image and discharge of the pH-sensitiveoptical filter agent by reduction of the pH substantially below the K ofsuch agent to thereby provide maximum reflectivity in terms of thepigment concentration present.

Alternatively, subsequent to discharge of the optical filter agent andprior to reduction of the pH to a paint where the dye developers arenon-diffusing, the system is buffered for a time sufiicient to permitsubstantial dye image formation.

The alkaline solution component of the processing composition,positioned intermediate the photosensitive element and theimage-receiving layer, thus permeates the emulsions to initiatedevelopment of the latent images contained therein. The respectiveassociated dye developers are immobilized or precipitated in exposedareas as a consequence of the development of the latent images. Thisimmobilization is apparently, at least in part, due to a change in thesolubility characteristics of dye developer upon oxidation andespecially as regards its solubility in alkaline solutions. It may alsobe due in part to a tanning effect on the emulsion by oxidizeddeveloping agent, and in part to a localized exhaustion of alkali as aresult of development. In unexposed and partially exposed areas of theemulsions, the associated dye developer is unreacted and diifusible andthus provides an imagewise distribution of unoxidized dye developerdissolved in the liquid processing composition, as a functon of thepoint-to-point degree of exposure of the silver halide emulsion. Atleast part of this image- Wise distribution of unoxidized dye developeris transferred, =by imbibition, to a superposed image-receiving layer orelement, said transfer substantially excluding oxidized dye developer.The image-receiving element receives a depthwise difiusion, from thedeveloped emulsion, of unoxidized dye developer Without appreciablydisturbing the imagewise distribution thereof to provide the reversed orpositive color image of the developed image.

Subsequent to distribution of processing composition 12, container 11may be manually dissociated from the remainder of the film unit, asdescribed above, to provide the product illustrated in FIG. 6-.

The present invention will be further illustrated and detailed inconjunction with the following illustrative constructions with set outrepresentative embodiments and photographic utilization of the novelphotographic film units of this invention, which, however, are notlimited to the details therein set forth and are intended to beillustrative only.

Film units similar to that shown in the drawings may be prepared, forexample, by coating, in succession, on a gelatin subbed, 4 mil opaquepolyethylene terephthalate film base, the following layers:

(1) A layer of the cyan dye developer 1,4-bis-(pl-[hydroquinonyl-ot-methyl]-ethylamino)-5,8 dihydroxy anthraquinonedispersed in gelatin and coated at a coverage of about 80 mgs./ft. ofdye and about 100 mgs./ft. of gelatin;

(2) A red-sensitive gelatino-silver iodobromide emulsion coated at acoverage of about 2215 mgs./ft. of silver and about 50 mgs./ft. ofgelatin;

(3) A layer of the acrylic latex sold by Rohm and and Haas Co.,Philadelphia, Pa., U.S.A., under the trade designation AC-6l andpolyacrylamide coated at a coverage of about 150 mgs/ft. of AC-61 andabout mgs./ ft. of polyacrylamide;

(4) A layer of the magenta dye developerZ-(p-[B-hydroquinonylethyl]-phenylazo)-4-isopropoxy-1 naphthol dispersedin gelatin and coated at a coverage of 70 mgs./ ft. of dye and about 120mgs./ft. of gelatin;

(5) A green-sensitive gelatino-silver iodobromide emulsion coated at acoverage of about 120 mgs./ft. of silver and 60 mgs./ft. of gelatin;

(6) A layer comprising the acrylic latex sold by Rohm and Haas Co. underthe trade designation B15 and polyacrylamide coated at a coverage ofabout 100 mgs./ft. of B-15 and about mgs./ft. of polyacrylamide;

(7) A layer of the yellow dye developer4-(p-U8-hydroquinonylethyl]-phenylazo)-3 (N,n hexylcarb0xamido)-l-phenyl-S-pyrazolone and the auxiliary developer 4'- methylphenylhydroquinone dispersed in gelatin and coated at a coverage of about 50mgs./ft. of dye, about mgs./ ft. of auxiliary developer and 50 mgs./ft.of gelatin;

(8) A blue-sensitive gelatino-silver iodobromide emulsion coated at acoverage of about 75 mgs/ft. of silver and about 75 mgs./ft. of gelatin;and

(9) A layer of gelatin coated at a coverage of about 50 mgs./ft. ofgelatin.

Then a transparent 4 mil polyethylene terephthalate film base may becoated, in succession, with the following illustrative layers:

(1) A 7:3 mixture, by weight, of polyethylene/maleic acid copolymer andpolyvinyl alcohol at a coverage of about 1400 mgs./ft. to provide apolymeric acid layer;

(2) A graft copolymer of acrylamide and diacetone acrylamide on apolyvinyl alcohol backbone in a molar ratio of 1:3.2z1 at a coverage ofabout 800 mgs/ftfi, to provide a polymeric spacer layer; and

3) A 2:1 mixture, by weight, of polyvinyl alcohol andpoly-4-vinylpyridine, at a coverage of about 900 mgs./ft. and includingabout 20 mgs./ft. phenyl mercapto tetrazole, and about 2X10 moles/ft. ofbenzoic acid (in methanol) to provide a polymeric image-receiving layerhaving associated therewith means adapted to discharge thelight-absorbing barrier.

The two components thus prepared may then be taped together in laminateform, at their respective edges, by means of a pressure-sensitivebinding tape extending around, in contact with, and over the edges ofthe resultant laminate.

A rupturable container comprising an outer layer of lead foil and aninner liner or layer of polyvinyl chloride retaining an aqueous alkalineprocessing solution compnsmg:

Water cc. Potassium hydroxide gms 11.2 Hydroxyethyl cellulose (highviscosity) [commercially available from Hercules Powder Co., Wilmington,Del., under the trade name Natrasol 250] grams 3.4N-phenethyl-a-picolinium bromide do 2.7 Benzotriazole do 1.15 Titaniumdioxide do 50.0 (A) 2.08

H 2 H /N OH N n-CuHu-O (B) Ems 0.52

m aa-n TABLE-Continued (C) gms 1.18

OH H C-CH;

may then be fixedly mounted on the leading edge of each of thelaminates, by pressure-sensitive tapes interconnecting the respectivecontainers and laminates, such that, upon application of compressivepressure to a container, its contents may be distributed, upon ruptureof the containers marginal seal, between the polymeric image-receivinglayer and next adjacent gelatin layer.

The photosensitive composite film units may be exposed through stepwedges to selectively filter radiation incident on the transparentpolyethylene terephthalate layer and processed by passage of the exposedfilm units through appropriate pressure-applying members, such assuitably gapped, opposed rolls, to effect rupture of the container anddistribution of its contents. During processing, the multicolor dyetransfer image formation may be viewed through the transparentpolyethylene terephthalate layer against the titanium dioxide backgroundprovided by distribution of the pigment containing processingcomposition between layer 9 and the polymeric image-receiving layer.Multicolor dye transfer image formation will be found to besubstantially completed and exhibiting the required color brilliance,hues, saturation and isolation, within a period of approximately 90seconds. The image formation may be immediately viewed upon distributionof the processing composition by reason of the protection againstincident radiation afforded the photosensitive silver halide emulsionlayers by the compositions optical transmission density of -6.0 densityunits and against the titanium dioxides effective reflective backgroundafforded by reason of the composition possessing an optical reflectiondensity -1.0 density units.

In an alternative embodiment, a film unit was constructed substantiallyas above except that the imagereceiving element did not contain benzoicacid and the processing solution additionally contained 5.7 g. of sodiumorthosiilcate. Similar results were obtained with this film unit as withthe above-described film unit.

The initial optical transmission density provided by a processingcomposition substantially as above at the respective Amax, of thelast-identified optical filter agents measure in situ as a compositeformulation comprises -6.2, 6.2 and 6.1, respectively, of which -1.25,1.15 and 1.10, respectively, is contributed by the titanium dioxidecontent of the processing composition, the remainder contributed by theoptical filter agents at a pH above their respective pK In the absenceof the titanium dioxide, the measured optical density provided by theoptical filter agents in combination at their respective A comprises-2.4, 2.05 and 2.3. It will be apparent that the optical densities ofthe optical filter agent individually added to the optical density ofthe titanium dioxide is insuflicient theoretically to provide therequired minimum optical transmission density of -6.0 density units, buthas been found, by means of the present invention, to unexpectedlyprovide in combination an optical density in accordance with the 24mathematical expression D =EC(l-|Al), wherein D is transmission density,E is the epsilon of the optical filter agent, C is the concentration andl is the radiation path length; thus directly providing the unexpectedadvantageous end results discussed in detail above.

The pH and solvent concentration of the alkaline processing solutioninitially empoyed must possess a pH above the K of the optical filteragents, that is, the pH at which about 50% of the agents are present asthe lesser absorbing species and about 50% are present as the greaterabsorbing species, preferably a pK of -11 and most preferably -l2 and apH at which the dye developers employed are soluble and diffusible.Although it has been found that the specific pH to be employed may bereadily determined empirically for any dye developer and optical filteragent, or group of dye developers and filter agents, most particularlydesirable dye developers are soluble at pHs above 9 and relativelyinsoluble at pHs below 9, in reduced form, and relatively insoluble atsubstantially any alkaline pH, in oxidized form, and the system can bereadily balanced accordingly for such dye developers. In addition,although as previously noted, the processing composition, in thepreferred embodiment, will include the stated film-formingviscosityincreasing agent, or agents, to facilitate spreading of thecomposition and to provide maintenance of the spread composition as astructurally stable layer of the laminate, subsequent to distribution,it is not necessary that such agent be employed as a component of thecomposition.

The pK s of the acidic additives are preferably only slightly lower thanthat of the particular optical filter agent in order to provide forrapid discharge of the light-absorbing medium.

Neutralizing means, for example, a polymeric acid layer of the typediscussed above will be incorporated, as stated, in the film unit of thepresent invention, to provide reduction of the alkalinity of theprocessing solution from a pH at which the dyes are diffusible to a pHat which the dyes are substantially nondilfusible, in order toadvantageously further stabilize and optimize refiectivity of the dyetransfer image. In such instance, the neutraliizng layer may compriseparticulate acid reacting reagent disposed within the film unit or apolymeric acid layer, for example, a polymeric acid layer approximating0.3 to 1.5 mils. in thickness, positioned intermediate the transparentsupport and image-receiving layer, and/or the opaque support and nextadjacent emulsion/dye unit layer, and the film unit may also contain apolymeric spacer or barrier layer, for example, approximating 0.1 to 0.7mil in thickness, next adjacent the polymeric acid layer, opposite therespective support layer, as previously described.

Specifically, the film units may employ the presence of a polymeric acidlayer such as, for example, of the type set forth in US. Pat. No.3,362,819 which, most preferably, includes the presence of an inerttiming or spacer layer intermediate the polymeric acid layer carried ona support and the image-receiving layer.

As set forth in the last-mentioned patent, the neutralizing layer maycomprise polymers which contain acid groups, such as carboxylic acid andsulfonic acid groups, which are capable of forming salts with alkalimetals, such as sodium, potassium etc., or with organic bases,particularly quaternary ammonium bases, such as tetramethyl ammoniumhydroxide, or potentially acid-yielding groups, such as anhydrides orlactones, or other groups which are capable of reacting with bases tocapture and retain them. The acid-reacting group is, of course, retainedin the polymer layer. In the preferred embodiments disclosed, thepolymer contains free carboxyl groups and the transfer processingcomposition employed contains a large concentration of sodium and/orpotassium ions. The acid polymers stated to be most useful arecharacterized by containing free carboxyl groups, being insoluble inwater in the free acid form, and by forming water-soluble sodium and/orpotassium salts. One may also employ polymers containing carboxylic acidanhydride groups, at least some of which preferably have been convertedto free carboxyl groups prior to imbibition. While the most readilyavailable polymeric acids are derivatives of cellulose or of vinylpolymers, polymeric acids from other classes of polymers may be used. Asexamples of specific polymeric acids set forth in the application,mention may be made of dibasic acid half-ester derivatives of cellulosewhich derivatives contain free carboxyl groups, e.g., cellulose acetatehydogen phthalate, cellulose acetate hydrogen glutarate, celluloseacetate hydrogen succinate, ethyl cellulose hydrogen succinate, ethylcellulose acetate hydrogen succinate, cellulose acetate hydrogensuccinate hydrogen phthalate; ether and ester derivatives or cellulosemodified with sulfoanhydrides, e.g., with ortho-sulfobenzoic anhydride;polystyrene sulfonic acid; carboxymethyl cellulose; polyvinyl hydrogenphthalate; polyvinyl acetate hydrogen phthalate; polyacrylic acid;acetals of polyvinyl alcohol with carboxy or sulfo substitutedaldehydes, e.g., m-, or p-benzaldehyde sulfonic acid or carboxylic acid;partial esters of ethylene/maleic anhydride copolymers; partial estersof methyl-vinyl ether/maleic anhydride copolymers; etc.

As previously noted, the pH of the processing composition preferably isof the order of at least 12 to 14 and the pKa of the selected opticalfilter agents will accordingly preferably be in the order of 13 orgreater. The polymer layer is disclosed to contain at least sufficientacid groups to effect a reduction in the pH of the image layer to a pHof at least 11 or lower at the end of the imbibition period, andpreferably to a pH of about to '8 within a short time after imbibition,thus requiring, of course, that the action of the polymeric acid beaccurately so controlled as not to interfere with either development ofthe negative or image transfer of unoxidized dye developers. For thisreason, the pH of the image layer must be kept at a functional transferlevel, for example, 12 to 14 until the dye image has been formed afterwhich the pH is reduced very rapidly to a pH below that at which dyetransfer may be accomplished, for example, at least about 11 andpreferably about pH 9 to 10. Unoxidized dye developers containinghydroquinonyl developing radicals diffuse from the negative to thepositive as the sodium or other alkali salt. The diffusion rate of suchdye image-forming components thus is at least partly a function of thealkali concentration, and it is necessary that the pH of the image layerremain on the order of, for example, 12 to 14- until transfer of thenecessary quantity of dye has been accomplished. The subsequent pHreduction, in addition to its desirable effect upon image lightstability, serves a highly valuable photographic function bysubstantially terminating further dye transfer.

In order to prevent premature pH reduction during transfer processing,as evidenced, for example, by an undesired reduction in positive imagedensity, the acid groups are disclosed to be so distributed in thepolymer layer that the rate of their availability to the alkali iscontrollable, e.g., as a function of the rate of swelling of the polymerlayer which rate in turn has a direct relationship to the diffusion rateof the alkali ions. The desired distribution of the acid groups in thepolymer layer may be effected by mixing acid polymer with a polymer freeof acid groups, or lower in concentration of acid groups, and compatibletherewith, or by using only an acid polymer but selecting one having arelatively lower proportion of acid groups. These embodiments areillustrated, respectively, in the cited copending application, by (a) amixture of cellulose acetate and cellulose acetate hydrogen phthalateand (b) a cellulose acetate hydrogen phthalate polymer having a muchlower percentage of phthalyl groups than the first-mentioned celluloseacetate hydrogen phthalate.

It is also there disclosed that the layer containing the polymeric acidmay contain a water-insoluble polymer,

preferably a cellulose ester, which acts to control or modulate the rateat which the alkali salt of the polymer acid is formed. As examples ofcellulose esters contemplated for use, mention is made of celluloseacetate, cellulose acetate butyrate, etc. The particular polymers andcombinations of polymers employed in any given embodiment are, ofcourse, selected so as to have adequate wet and dry strength and whennecessary or desirable, suitable subcoats are employed to help thevarious polymeric layers adhere to each other during storage and use.

The inert spacer layer of the last-mentioned patent, for example, aninert spacer layer comprising polyvinyl alcohol or gelatin, acts to timecontrol the pH reduction by the polymeric acid layer. This timing isdisclosed to be a function of the rate at which the alkali diffusesthrough the inert spacer layer. It is there stated to have been foundthat the pH does not drop until the alkali has passed through the spacerlayer, i.e., the pH is not reduced to any significant extent by the merediffusion into the interlayer, but the pH drops quite rapidly once thealkali diffuses through the spacer layer.

As disclosed in aforementioned US. Pat. No. 3,362,819, the presence ofan inert spacer layer was found to be effective in evening out thevarious reaction rates over a wide range of temperatures, for example,by preventing premature pH reduction when imbibition is effected attemperatures above room temperature, for example, at to F. By providingan inert spacer layer, that application discloses that the rate at whichalkali is available for capture in the polymeric acid layer becomes afunction of the alkali diffusion rates.

However, as disclosed in US. Pat. No. 3,455,686 preferably theaforementioned rate at which the cations of the alkaline processingcomposition, i.e., alkali ions, are available for capture in thepolymeric acid layer should be decreased with increasing transferprocessing tempera tures in order to provide diffusion transfer colorprocessess relatively independent of positive transfer image variationsover an extended range of ambient temperatures.

Specifically, it is there stated to have been found that the diffusionrate of alkali through a permeable inert polymeric spacer layerincreases with increased processing temperature to the extent, forexample, that at relatively high transfer processing temperatures, thatis, transfer processing temperatures above approximately 80 F., apremature decrease in the pH of the transfer processing compositionoccurs due, at least in part, to the rapid diffusion of alkali from thedye transfer environment and its subsequent neutralization upon contactwith the polymeric acid layer. This was stated to be especially true ofalkali traversing an inert spacer layer possessing permeability toalkali optimized to be effective with the temperature range of optimumtransfer processing. Conversely, at temperature below the optimumtransfer processing range, for example, temperatures below approximately40 F., the last-mentioned inert spacer layer was disclosed to provide aneffective diffusion barrier timewise preventing effective traverse ofthe inert spacer layer by alkali having temperature depressed diffusionrates and to result in maintenance of the transfer processingenvironments high pH for such an extended time interval as to facilitateformation of transfer image stain and its color definition.

It is further stated in the last-mentioned US. Pat. No. 3,455,686 tohave been found, however, that if the inert spacer layer of theprint-receiving element is replaced by a spacer layer which comprises apermeable polymeric layer exhibiting permeability inversely dependent ontemperature, that is, a polymeric film-forming material which exhibitsdecreasing permeability to solubilized alkali derived cations such asalkali metal and quaternary ammonium ions under conditions of increasingtemperature, that the positive transfer image defects resultant from theaforementioned overextended pH maintenance and/or premature pH reductionare obviated.

As examples of polymers which were disclosed to exhibit inversetemperature-dependent permeability to alkali, mention may be made of:hydroxypropyl polyvinyl alcohol, polyvinyl methyl ether, polyethyleneoxide, polyvinyl oxazolidone, hydroxypropyl methyl cellulose, isopropylcellulose, partial acetals of polyvinyl alcohol such as partialpolyvinyl butyral, partial polyvinyl formal, partial polyvinyl acetal,partial polyvinyl propional, and the like.

The last-mentioned specified acetals of polyvinyl were stated togenerally comprise saturated aliphatic hydrocarbon chains of a molecularweight of at least 1000, preferably of about 1000 to 50,000, possessinga degree of acetalation within about 10 to 30%, 10 to 30%, 20 to 80%,and 10 to 40%, of the polyvinyl alcohols theoretical polymeric hydroxygroups, respectively, and including mixed acetals where desired.

Where desired, a mixture of the polymers is to be employed, for example,a mixture of hydroxypropyl methyl cellulose and partial polyvinylbutyral.

Employment of the detailed and preferred film units of the presentinvention, according to the herein described color diffusion transferprocess, specifically provides for the production of a highly stabletransfer image accomplished, at least in part, by effectively obviatingthe previously discussed disadvantages of the prior art products andprocesses, by in process adjustment of the environmental processingcomposition solvent concentration from a solvent concentration at whichdye diffusion or transfer is operative to a solvent concentration atwhich dye transfer is inoperative subsequent to substantial transferimage formation. The stable color transfer image is obtainedirrespective of the fact that the film unit is maintained as an integrallaminate unit during exposure, processing, viewing, and storage of theunit. Accordingly, by means of the present invention, multicolortransfer may be provided over an extended processing temperature rangewhich exhibit desired maximum and minimum dye transfer image densities;yellow, magenta and cyan dye saturation; red, green and blue hues; andcolor separation. These unexpected advantages are in addition to themanufacturing advantages obtained by reason of the present inventionsintegral color transfer film unit and which will be readily apparentfrom examination of the units parameters, that is, for example,advantages in more efficient utilization of fabricating materials andcomponents, enhanced simplicity of film manufacture and camera designand construction, and more simplified and effectively controlledcustomer utilization of the unit.

The dimensionally stable support layers referred to may comprise any ofthe various types of conventional opaque and transparent rigid orflexible materials possess ing the requisite liquid impermeability andvapor transmissivity denoted above, and may comprise polymeric films ofboth synthetic types and those derived from naturally occurringproducts. Particularly suitable materials include aqueous alkalinesolution impermeable, water vapor permeable, flexible polymericmaterials such as vapor permeable polymeric films derived from ethyleneglycol terephthalic acid, vinyl chloride polymers; polyvinyl acetate;polyamides; polymethacrylic acid methyl and ethyl esters; cellulosederivatives such as cellulose, acetate, triacetate, nitrate, propionate,butyrate, acetatepropionate, or acetate-butyrate; alkaline solutionimpermeable, water vapor permeable papers; crosslinked polyvinylalcohol; regenerated cellulose; and the like.

As examples of materials, for use as the image-receiving layer, mentionmay be made of solution dyeable polymers such as nylon as, for example,N-methoxymethyl polyhexamethylene adipamide; partially hydrolyzedpolyvinyl acetate; polyvinyl alcohol with or without plasticizers;cellulose acetate with filler as, for example, one-half celluloseacetate and one-half oleic acid; gelatin; and other materials of asimilar nature. Preferred materials comprise polyvinyl alcohol orgelatin containing a dye 28 mordant such as poly-4-vinylpyridine, asdisclosed in U.S. Pat. 3,148,061, issued Sept. 8, 1964.

It will be noted that the liquid processing composition employed maycontain an auxiliary or accelerating developing agent, such asp-methylaminophenol, 2,4-diaminophenol, p-benzylaminophenyl,hydroquinone, toluhydroquinone, phenylhydroquinone,4-methylphenylhydroquinone, etc. It is also contemplated to employ aplurality of auxiliary or accelerating developing agents, such as a 3-pyrazolidone developing agent and a benzenoid developing agent, asdisclosed in U.S. Pat. No. 3,039,869, issued June 19, 1962. As examplesof suitable combinations of auxiliary developing agents, mention may bemade of 1- phenyl-3-pyrazolidone in combination with p-benzylaminophenoland 1-phenyl-3-pyrazolidone in combination with2,S-bis-ethylenimino-hydroquinone. Such auxiliary developing agents maybe employed in the liquid processing composition or they may beinitially incorporated, at least in part, in any one or more of thesilver halide emulsion strata, the strata containing the dye developers,the interlayers, the overcoat layer, the image-receiving layer, or inany other auxiliary layer, or layers, of the film unit. It may be notedthat at least a portion of the dye developer oxidized during developmentmay be oxidized and immobilized as a result of a reaction, e.g., anenergy-transfer reaction, with the oxidation product of an oxidizedauxiliary developing agent, the latter developing agent being oxidizedby the development of exposed silver halide. Such a reaction of oxidizeddeveloping agent with unoxidized dye developer would regenerate theauxiliary developing agent for further reaction with the exposed silverhalide.

In addition, development may be effected in the presence of an oniumcom-pound, particularly a quaternary ammonium compound, in accordancewith the processes disclosed in U.S. Pat. No. 3,173,786, issued Mar. 16,1965.

It will be apparent that the relative proportions of the agents of thediffusion transfer processing composition may be altered to suit therequirements of the operator. Thus, it is within the scope of thisinvention to modify the herein described developing compositions by thesubstitution of preservatives, alkalies, etc., other than thosespecifically mentioned, provided that the pH of the composition isinitially at the first pH and solvent concentration required. Whendesirable, it is also contemplated to include, in the developingcomposition, components such as restrainers, accelerators, etc.Similarly, the concentration of various components may be varied over awide range and when desirable adaptable components may be disposed inthe photosensitive element, prior to exposure, in a separate permeablelayer of the photosensitive element and/ or in the photosensitiveemulsion.

In all examples of this specification, percentages of components aregiven by weight unless otherwise indicate An extensive compiliation ofspecific dye developers particularly adapted for employment inphotographic diffusion transfer processes is set forth in aforementionedU.S. Pat. No. 2,983,606 and in the various copending U.S. applicationsreferred to in that patent, especially in the table of U.S. applicationsincorporated by reference into the patent as detailed in column 27. Asexamples of additional U.S. patents detailing specific dye developersfor photographic transfer process use, mention may also be made of U.S.Pats. Nos. 2,983,605, 2,992,106; 3,047,- 386; 3,076,808; 3,076,820;3,077,402; 3,126,280; 3,131,- 061; 3,134,762; 3,134,765; 3,135,604;3,135,605; 3,135,- 606; 3,135,734; 3,141,772; 3,142,565; and the like.

As additional examples of synthetic, film-forming, permeable polymersparticularly adapted to retain dispersed dye developer, mention may bemade of nitrocarboxymethyl cellulose, as disclosed in U.S. Pat. No.2,992,104; an acylamidobenzene sulfo ester of a partial sulfobenzal ofpolyvinyl alcohol, as disclosed in U.S. Pat. No. 3,043,- 692; polymersof N-alkyl-a,fi-unsaturated carboxamides and copolymers ofN-alkyl-a,p-carboxamides with N-hydroxyalkyl-ot,fi-unsaturatedcarboxamides, as disclosed in US. Pat. No. 3,069,263; copolymers ofvinylphthalimide and a,,8-unsaturated carboxylic acids, as disclosed inU.S. Pat. No. 3,061,428; copolyrners of N-vinylpyrrolidones and:,f3-UIIS3'LUI31J6d carboxylic acids and terpolymers ofN-vinylpyrrolidones, a,fl-unsaturated carboxylic acids and alkyl estersof a ti-unsaturated carboxylic acids, as disclosed in US. Pat. No.3,044,873; copolymers of N,N-di alkyl-a,,8-unsaturated carboxamides witho e-unsaturated carboxylic acids, the corresponding amides of suchacids, and copolymers of N-aryl and N-cycloalkyl-a,B-unsaturatedcarboxamides with anti-unsaturated carboxylic acids, as disclosed in US.Pat. No. 3,069,296; and the like.

In addition to conventional techniques for the direct dispersion of aparticulate solid material in a polymeric, or colloidal, matrix such asball-milling and the like techniques, the preparation of the dyedeveloper dispersion may also be obtained by dissolving the dye in anappropriate solvent, or mixture of solvents, and the resultant solutiondistributed in the polymeric binder, with optional subsequent removal ofthe solvent, or solvents, employed, as, for example, by vaporizationwhere the selected solvent, or solvents, possesses a sufficiently lowboiling point or washing where the selected solvent, or solvents,possesses a sufficiently high differential solubility in the washmedium, for example, water, when measured against the solubility of theremaining composition components, and/ or obtained by dissolving boththe polymeric binder and dye in a common solvent.

For further detailed treatment of solvent distribution systems of thetypes referred to above, and for an extensive compilation of theconventional solvents traditionally employed in the art to effectdistribution of photographic color-providing materials in polymericbinders, specifically for the formation component layers of photographicfilm units, reference may be made to US. Pats. Nos. 2,269,158;2,322,027; 2,304,939; 2,304,940; 2,801,171; and the like.

Although the invention has been discussed in detail throughout employingdye developers, the preferred image-providing materials, it will bereadily recognized that other, less preferred, image-providing materialsmay be substituted in replacement of the preferred dye developers in thepractice of the invention. For example, there may be employed dyeimage-forming materials such as those disclosed in US. Pats. Nos.2,647,049; 2,661,293; 2,698,244; 2,698,798; 2,802,735; 3,148,062;3,227,550; 3,227,551; 3,227,552; 3,227,554; 3,243,294; 3,330,655;3,347,671; 3,352,672; 3,364,022; 3,443,939; 3,443,940; 3,443,941;3,443,943; etc., wherein color diffusion transfer processes aredescribed which employ color coupling techniques comprising, at least inpart, reacting one or more color developing agents and one or more colorformers or couplers to provide a dye transfer image to a superposedimage-receiving layer and those disclosed in US. Pats. Nos. 2,774,668and 3,087,817, wherein color diffusion transfer processes are describedwhich employ the imagewise differential transfer of complete dyes by themechanisms therein described to provide a transfer dye image to acontiguous image-receiving layer, and thus including the employment ofimage-providing materials in whole or in part initially insoluble ornondiffusible as disposed in the film unit which diffuse duringprocessing as a direct or indirect function of exposure.

For the production of the photosensitive gelatino silver halideemulsions employed to provide the film unit, the silver halide crystalsmay be prepared by reacting a watersoluble silver salt, such as silvernitrate, with at least one water-soluble halide, such as ammonium,potassium or sodium bromide, preferably together with a correspondingiodide, in an aqueous solution of a peptizing agent such as a colloidalgelatin solution; digesting the dispersion at an elevated temperature,to provide increased crystal growth; washing the resultant water-solublesalts 30 by chilling the dispersion, noodling the set dispersion, andwashing the noodles with cold water, or altetrnatively, employing any ofthe various floc systems, or procedures, adapted to effect removal ofundesired components, for example, the procedures described in US. Pats.Nos. 2,614,928; 2,614,929; 2,728,662; and the like; afterripening thedispersion at an elevated temperature in combination with the additionof gelatin and various adjuncts, for example, chemical sensitizingagents of US. Pats. Nos. 1,574,944; 1,623,499; 2,410,689; 2,597,856;2,597,915; 2,487,850; 2,518,698; 2,521,926; and the like; all accordingto the traditional procedures of the art, as described in Neblette, C.B., Photography Its Materials and Processes, 6th ed., 1962.

Optical sensitization of the emulsions silver halide crystals may beaccomplished by contact of the emulsion composition with an effectiveconcentration of the selected optical sensitizing dyes dissolved in anappropriate dispersing solvent such as methanol, ethanol, acetone,water, and the like; all according to the traditional procedures of theart, as described in Hammer, F. M., The Cyanine Dyes and RelatedCompounds.

Additional optional additives, such as coating aids, hardeners,viscosity-increasing agents, stabilizers, preservatives, and the like,for example, those set forth hereinafter, also may be incorporated inthe emulsion formulation, according to the conventional procedures knownin the photographic emulsion manufacturing art.

The photoresponsive material of the photographic emulsion will, aspreviously described, preferably comprise a crystal of silver, forexample, one or more of the silver halides such as silver chloride,silver iodide, silver bromide, or mixed silver halides such as silverchlorobromide, silver chloroiodobromide or silver iodobromide, ofvarying halide ratios and varying silver concentrations.

As the binder for the respective emulsion strata, the aforementionedgelatin may be, in Whole or in part, replaced with some other colloidalmaterial such as albumin; casein; or zein; or resins such as a cellulosederivatives, as described in US. Pats. Nos. 2,322,085 and 2,327,808;polyacrylamides, as described in US. Pat. No. 2,541,474; vinyl polymerssuch as described in an extensive multiplicity of readily available US.and foreign patents.

In preferred embodiments of the present invention, the photosensitivesilver halide emulsions employed will be emulsions adapted to provide aDiffusion Transfer Process Exposure Index -50, which index indicates thecorrect exposure rating of a diffusion transfer color process at whichan exposure meter, calibrated to the ASA Exposure Index, must be set inorder that it give correct exposure data for producing color transferprints of satisfactorily high quality. The Diffusion Transfer ProcessExposure Index is based on a characteristic H&D* curve relating originalexposure of the photosensitive silver halide emulsions to the respectivecurve densities forming the resultant transfer image. Thus, theDiffusion Transfer Exposure Index is based on the exposure to which thephotosensitive silver halide emulsions, for use in color diffusiontransfer processes, must be subjected in order to obtain an acceptablecolor transfer image by that process and is a direct guide to theexposure setting to be entered in a camera in order to obtain properexposure of the film unit.

Although the preceding description of the invention has been couched interms of the preferred photosensitive component construction wherein atleast two selectively sensitized photosensitive strata are in contiguouscoplanar relationship and, specifically, in terms of the preferredtripack type structure comprising a red-sensitive silver halide emulsionstratum, a green-sensitive silver halide emulsion stratum and ablue-sensitive silver halide emulsion stratum having associatedtherewith, respectively a cyan dye developer, a magenta dye developerand a yellow dye developer, the photosensitive component of the filmunit may comprise at least two sets of selectively sensitized 31 minutephotosensitive elements arranged in the form of a photosensitive screenwherein each of the minute photosensitive elements has associatedtherewith, for example, an appropriate dye developer in or behind itsrespective silver halide emulsion portion. In general, a suitablephotosensitive screen will comprise minute red-sensitized emulsionelements, minute green-sensitized emulsion elements and minuteblue-sensitized emulsion elements arranged in side-by-side relationshipin a screen pattern and having associated therewith, respectively, acyan, a magenta and a yellow dye developer.

The present invention also includes the employment of a black dyeimage-providing material and the use of a mixture of dye image-providingmaterial adapted to provide a black-and-white trnasfer image, forexample, the employment of dye developers of the three subtractivecolors in an appropriate mixture in which the quantities of the dyedevelopers are proportioned such that the colors combine to provideblack.

Where in the specification, the expression positive image has been used,this expression should not be interpreted in a restrictive sense sinceit is used primarily for purposes of illustration, in that it definesthe image produced on the image-carrying layer as being reversed, in thepositive-negative sense, with respect to the image in the photosensitiveemulsion layers. As an example of an alternative meaning for positiveimage, assume that the photosensitive element is exposed to actiniclight through a negative transparency. In this case, the latent image inthe photosensitive emulsion layers will be a positive and the dye imageproduced on the image-carrying layer will be a negative. The expressionpositive image" is intended to cover such an image produced on theimage-carrying layer.

It will be recognized that, by reason of the preferred film unitsstructural parameters, the transfer image formed upon directed exposureof the film unit to be selected subject and processing, will be ageometrically reversed image of the subject. Accordingly, to providetransfer image formation geometrically nonreversed, exposure of suchfilm unit should be accomplished through an image reversing opticalsystem such a camera possessing an image reversing optical system.

In addition to the described essential layers, it will be recognizedthat the film unit may also contain one or more subcoats or layers,which, in turn, may contain one or more additives such as plasticizers,intermediate essential layers for the purpose, for example, of improvingadhesion, and that any one or more of the described layers may comprisea composite of two or more strata of the same, or different, componentsand which may be contiguous, or separated from, each other, for example,two or more neutralizing layers or the like, one of which may bedisposed intermediate the cyan dye image-forming component retaininglayer and the dimensionally stable opaque layer.

Since certain changes may be made in the above product and processwithout departing from the scope of the invention herein involved, it isintended that all matter contained in the above description or shown inthe accompanying drawings shall be interpreted as illustrative and notin a limiting sense.

What is claimed is:

1. A photographic film unit which comprises a plurality of sequentiallayers including a layer opaque to incident actinic radiation; aphotosensitive silver halide layer having associated therewithimage-forming material which is processing composition ditfusible at afirst pH as a function of the point-to-point degree of silver halidelayer exposure to incident actinic radiation; a layer adapted to receiveimage-forming material diffusing thereto; means for interposing,intermediate the silver halide layer and the reception layer, aninorganic reflecting pigment dis- Persion comprising at east one opticalfilter agent at a pH above the pK of said optical filter agent whose pKis below said first pH and above a second pH, in a concentrationelfective to provide a layer exhibiting optical transmission densitysufficient to provide a barrier to incident radiation actinic to thephotosensitive silver halide layer and means for reducing the initial pHof the film unit at the location of the optical filter agent to a secondpH below the K of the optical filter agent, said imageforming materialbeing dilfusible at said initial pH and said second pH, and, subsequentto substantial diffusion of image-forming material to the layer adaptedto receive image-forming material diffusing thereto, means for reducingthe pH of the film unit at the location of the image-forming material toa third pH wherein said imageforming material is substantiallynonditfusible.

2. A photographic film unit as defined in claim 1 wherein said means forproviding said barrier comprises a processing composition permeablelayer, intermediate the silver halide layer and the reception layer,which includes an inorganic light-reflecting pigment dispersioncontaining at least one pH sensitive dye at a pH below the pK of the dyeand a concentration etfective upon contact with a processing compositionpossessing a pH above the pK,, of the dye to provide a layer exhibitingoptical transmission density 3-6.0 density units and optical reflectiondensity L-l.0 density units.

3. A photographic film unit as defined in claim 2 wherein the means forintroducing the photographic processing composition comprises arupturable container retaining the processing composition positionedextending transverse an edge of the film unit, whereby application ofcompressive pressure to the container, discharges the containersprocessing composition contents intermediate the silver halide layer andthe reception layer.

4. A photographic film unit as defined in claim 1 wherein theimage-forming material is a dye image-forming material.

5. A photographic film unit as defined in claim 4 wherein the dyeimage-forming material comprises a dye which is a silver halidedeveloping agent.

6. A photographic film unit as defined in claim 5 including,intermediate the opaque layer and the reception layer, at least twoselectively sensitized silver halide emulsion layers each having a dyewhich is a silver halide developing agent of predetermined colorassociated therewith, each of the dyes soluble and diffusible inprocessing A composition at said first and second pH as a function ofthe point-to-point degree of exposure of the respective emulsionassociated therewith.

7. A photographic film unit as defined in claim 6 wherein each of theselectively sensitized silver halide emulsion layers possessespredominant spectral sensitivity to regions of the spectrum and the dyeassociated with each of said silver halide emulsion layers possesses aspectral absorption range subsequent to processing subtantiallycomplementary to the predominant ensitivity image of its associatedemulsion layer.

8. A photographic film unit as defined in claim 7 wherein at least oneoptical filter agent exhibits, at a pH above its pK major spectralabsorption in the spectral region within which a selectively sensitizedsilver halide emulsion layer possesses predominant spectral sensitivity.

9. A photographic film unit as defined in claim 1 wherein the pH abovethe pK,, of the filter agent is an alkaline pH above 7.

10. A photographic film unit as defined in claim 9 including at leastone layer positioned in the film unit and adapted to reduce the pH of anaqueous alkaline processing solution to said third pH at which the dyeis substantially nondilfusible subsequent to substantial transfer of dyeto the reception layer.

11. A photographic film unit as defined in claim 1 wherein said meansfor reducing the pH of the film unit

